This invention relates generally to an autofeed screwdriver for driving collated screws which are joined together in a strip, and, more particularly, to driving screws with flat bottom heads.
Collated screwstrips are known in which the screws are connected to each other by a retaining strip of plastic material. Such strips are taught, for example, by U.S. Pat. No. 4,167,229 issued Sep. 11, 1979 and its related Canadian Patents 1,040,600 and 1,054,982 as well as the present applicant""s U.S. Pat. No. 4,930,630, U.S. Pat. No. 5,542,323, U.S. Pat. No. 5,699,704, U.S. Pat. No. 5,758,768, U.S. Pat. No. 5,819,609 and U.S. Pat. No. 6,074,149, the disclosures of which are incorporated herein by reference. Screws carried in such screwstrips are adapted to be successively incrementally advanced to a position in alignment with and to be engaged by a bit of a reciprocating, rotating power screwdriver and screwed into a workpiece. In the course of the bit engaging the screws and driving it into a workpiece, the screw becomes detached from the plastic strip leaving the strip as a continuous length.
In the use of such collated screwstrips in screwdrivers, the strip serves a function of assisting in guiding the screw into a workpiece and, to accomplish this, the strip is retained against movement towards the workpiece. In the screwstrip, each screw to be driven has its threaded shaft threadably engaged in a threaded sleeve of the strip such that on the screwdriver engaging and rotating each successive screw, the screw turns within the sleeve which acts to guide the screw as it moves forwardly into threaded engagement into the workpiece. Preferably, only after the tip of the screw becomes engaged in the workpiece, does the head of the screw come into contact with the sleeves. Further, forward movement of the screw into the workpiece then draws the head downwardly to engage the sleeve and to rupture the sleeve by reason of the forward movement of the head with the strip retained against movement towards the workpiece. The sleeve preferably is configured to have fragile strips which break on the head passing through the sleeve such that the strip remains intact as a continuous length. Since the strip is a continuous length, on advancing the screwstrip with each successive screw to be driven, it necessarily results that a spent portion of the strip from which each screw has been driven are also advanced to exit from the power screwdriver.
Known autofeed screwdrivers for driving such collated screwstrips include U.S. Pat. No. 4,146,071 to Mueller et al, issued Mar. 27, 1976, U.S. Pat. No. 5,186,085 to Monaceli, issued Feb. 16, 1993, U.S. Pat. No. 5,433,129 to Reusch et al, issued Jul. 18, 1995 and the present applicant""s U.S. Pat. Nos. 5,568,753; 5,855,151; 5,927,163; 5,870,933; 5,934,162 and 6,089,132, the disclosures of which are incorporated herein by reference. Such known screwdrivers include a rotatable and reciprocally moving screwdriver shaft which is turned in rotation by an electric motor. A screwdriving bit forms a forwardmost portion of the shaft for engaging the head of each successive screw as each screw is moved into a driving position, axially aligned under the screwdrive shaft.
Known autofeed screwdrivers suffer the disadvantage that the retaining strip from which a screw is desired to be separated is not always adequately deflected laterally with the result that the strip becomes caught under the head of the screw being driven and/or jamming of the autofeed screwdriver. This disadvantage is particularly acute with screws having heads with flat bottomed under surfaces. The disadvantage increases as the diameter of the flat bottomed under surfaces of such flat heads increases.
U.S. Pat. No. 5,433,129 to Reusch et al, issued Jul. 18, 1995 and published Canadian patent application 2,264,391 to Muro, published Jan. 1, 1999, both suggest mechanical arrangements to overcome this problem using pivotally mounted lever mechanisms. The devices suggested by these patents are cumbersome and subject to mechanical failure.
To at least partially overcome these disadvantages of the prior art, the present invention provides an autofeed screwdriver with a deflecting bar which slides substantially axially relative the driver shaft and deflects the spent strip laterally to one side away from a screw being driven.
An object of the present invention is to provide a simple mechanism which urges a screwstrip laterally away from a screw being driven.
Another object is to urge a screwstrip holding, a screw to be driven to twist about the longitudinal of the strip in a desired direction.
Another object is to provide a method of driving screws collated in a screwstrip by urging the strip to twist with the rear of the strip facing the under surface of the head of the screw to deflect away from the screw.
Accordingly, in one aspect, the present invention provides an apparatus for driving with a power driver a screwstrip comprising threaded fasteners such as screws or the like, which are joined together in a strip comprising:
a housing;
an elongate driver shaft for operative connection to a power driver for rotation thereby and defining a longitudinal axis;
the driver shaft and housing coupled together for movement together in unison parallel the axis of the driver shaft,
a slide body coupled to the housing for displacement relative the housing and driver shaft parallel to the axis of the driver shaft between an extended position and a retracted position;
a spring biasing the slide body forwardly relative to the housing parallel the axis to the extended position;
the slide body having a guideway therethrough to receive successive screws therein in coaxial alignment with the driver shaft;
the driver shaft having at a forward end a bit,
the driver shaft reciprocally axially movable in the guideway in movement of the slide body between the extended position and the retracted position to engage a screw carried on the strip in the guideway with the bit and drive the screw axially forwardly in the guideway severing the screw from the strip while maintaining the length of the strip substantially intact;
the slide body having a guide channel for the screwstrip extending through the slide body transverse to the guideway and intersecting with the guideway;
the guide channel opening into the guideway on a first side thereof as a screw-and-strip entranceway;
the guide channel exiting from the guideway on a second side thereof opposite the entranceway as a strip exitway;
the entranceway and exitway juxtapositioned to permit screws collated in a strip spaced in parallel relation to each other to be successively advanced along an advance line of the guide channel through the entranceway into the guideway to locate each successive screw within the guideway for driving therefrom and with spent portions of the strip from which screws have been severed to extend from the guideway via the exitway;
a strip displacing bar mounted to the housing for sliding with the housing parallel the axis,
the bar carried on the housing for movement relative the slide body axially of the slide body transversely across the exitway between a position rearward of the exitway where the bar does not engage the spent strip which extends from the exitway and forward positions in which the bar engages the spent strip and deflects the spent strip laterally away from the screw being driven in a direction substantially transverse to both the axis and the advance line.
In another aspect, the present invention provides a method of driving a screw from a screwstrip comprising a plurality of screws held in a plastic strap in spaced parallel relation, the strap comprising an elongate continuous member with the screws on one side of the strap,
the strap having a rear edge directed towards the head of the screws, the method comprising: engaging a screw to be driven with a bit of a driver, holding the strap against forward movement; and
after engaging the head of the screw to be driven with the bit, twisting the spent strip from which screws have been driven to urge a rear edge of the strip closest the head of the screw laterally away from the screw.